The present invention relates to a circuit breaker trip actuator, and, more particularly, to a fast acting, high force trip actuator.
Modem circuit breakers rely on electronics for the detection of potentially damaging over-current conditions. These electronics, known as trip units, sense current in a protected portion of an electrical distribution circuit and initiate a trip signal if the sensed current indicates an over-current condition. In such circuit breakers, an electromechanical actuator, known as a trip actuator or trip mechanism, is used to unlatch a circuit breaker operating mechanism in response to the trip signal. The operating mechanism is a spring-operated linkage arrangement. When unlatched, the operating mechanism separates a pair of main contacts to stop the flow electrical current to the protected portion of the distribution circuit. The operation of such circuit breakers is well known.
During the operation of the circuit breaker, it is desirable to part the main contacts is fast is possible after a trip signal is given by the electronic trip unit. Opening the contacts faster minimizes the arcing energy seen by the main contact structure, prolonging contact life.
The trip actuator is responsible for a large part of the time required in releasing these contacts. Typically, a trip actuator includes a solenoid or flux shifter that pushes or releases an actuating arm in response to the trip signal. The trip actuator also typically includes a mechanical linkage arrangement that translates the action of the actuating arm into a force that will unlatch the operating mechanism.
Increases in the speed or power of trip actuators have been accomplished through the use of a larger solenoid or flux shifter. However, the use of a larger solenoid or flux shifter requires that the trip unit to provide a higher firing voltage (trip signal) to the solenoid or flux unit. In addition, the larger solenoid or flux unit requires a greater amount of space in a tight circuit breaker housing.